Description and Demonstration of an Artificial Larynx

Abstract

A description is given of the normal vocal tract and the action of the vocal cords in generating sound waves from the steady flow of air from the lungs. For persons whose larynx has been removed the flow of air from the lungs is changed into sound by a device external to the body and this sound is converted into speech by introducing it into the mouth and carrying on the ordinary speech-producing motions with the lips, tongue, teeth, etc. A description is given of a recently developed vibrating reed type of artificial larynx for accomplishing the above. While using this instrument for producing a sustained vowel the rate of expulsion of air is about 125 cc per second and the excess pressure in the lungs is about .005 atmospheres, giving the rate at which the lungs do work as .06 watts. Using Saccia's measurements of the rate of radiation of acoustic energy from the lips of a speaker it is calculated that of the energy used by the lungs in forcing air through the glottis only about 0.17% is converted into useful acoustic energy.